Apparatus and procedure for trapping embolic debris

ABSTRACT

A collapsible and deployable filter for blocking debris and passing blood in a blood vessel in a patient&#39;s body, the filter including; a framework of a flexible material, constructed to have a radially compressed state, in which the framework is radially compressed by radial deforming forces, and a radially expanded state to obdurate an artery; and a flexible filter material secured to said framework and having pores dimensioned to prevent the passage of debris therethrough while allowing the passage of blood. The filter has, in the radially expanded state of the framework, a generally conical or frustoconical form with a large diameter end, a small diameter end opposite to the large diameter end, and a side surface extending between the ends. The filter has an opening that is free of filter material at the small diameter end or in the side surface.

BACKGROUND OF THE INVENTION

The present invention relates to an apparatus and procedure for aidingmedical treatments in the blood circulation system of a patient, and inparticular for preventing the circulation of embolic debris, or bloodclots, resulting from such treatments. The invention is primarily, butnot exclusively, concerned with providing protection in connection withprocedures like those for implanting a prosthetic heart valve.

There are known procedures, known as transcatheter aortic valveimplantation (TAVI), in which a prosthetic heart valve is implanted atthe site of a defective native valve, or of a previously implanteddefective prosthetic valve. In these procedures, the new prostheticvalve and its guiding structure are introduced by a transcutaneouscatheterization technique. For example, for implanting a prostheticaortic heart valve, the valve and delivery components will be introducedthrough an incision in the groin or arm and along a blood vessel path tothe desired location.

Such a procedure is disclosed, for example, in U.S. Pat. No. 7,585,321,which issued to Alan Cribier on Sep. 8, 2009, the entire disclosure ofwhich is incorporated herein by reference. Such valves and theirassociated guiding devices are marketed by Medtronic and by EdwardsLifesciences, one example of the Edwards valves being marketed under thetrade name Sapien.

Although such prosthetic valves have been used successfully to provide areplacement for stenotic native heart valves or defective prostheticvalves, the implantation procedure can result in the creation of embolicdebris, which will flow downstream through the circulatory system andwill, in a certain percentage of cases, cause blockages in smaller bloodvessels.

BRIEF SUMMARY OF INVENTION

The present invention provides an apparatus and procedure to prevent thecirculation of embolic debris resulting from procedures carried out inthe blood circulatory system, one such procedure being, for example, theimplantation of a prosthetic heart valve.

To this end, the invention provides a novel filter and a novelcombination of such filter and a blocking device for trapping embolicdebris produced during such a medical procedure. It also provides thefilter with a central, or axial, orifice through which the valveimplantation device, or system, can be directed, which facilitates thisprocess and reduces the traumatic effects of the valve implantationdevice on the wall of the aorta. Since it is known that trauma to theaortic wall generates clots and calcium, the position of the orifice inthe filter acts as a landmark and facilitates atraumatic entry of thevalvular device.

The invention also provides, together with the filter and blockingdevice, a stent or stent graft that is preliminarily deployed againstthe inner wall of the blood vessel, e.g., the aorta, to prevent traumaduring introduction of the filter.

In further accordance with the invention, the filter can be deliveredin, deployed from and retracted into, a known radially expandable sheathprovided particularly to facilitate retraction of the filter.

In further accordance with the invention, there is provided a filtersystem for preventing the flow of debris in the pulmonary artery duringheart surgery, such as congenital heart surgery.

The components of embodiments of the invention may be conveyed to thetreatment site along various blood vessel paths and may all beintroduced via the same path or via respectively different paths. Forexample, if the components are to be positioned in, or pass through, theaorta, the, or each, component can be introduced through an incision ina groin and the associated femoral artery, or through an incision in anarm and the associated subclavian artery.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an embodiment of a filter according tothe present invention.

FIG. 2 is a perspective and partly cross-sectional view of the filtershown in FIG. 1, together with related components and a heart valvedelivery system.

FIGS. 3 and 4 are views similar to those FIGS. 1 and 2 of a secondembodiment of the present invention.

FIG. 5 is a cross-sectional view relating to a third embodiment of theinvention.

FIG. 6 is a view, partly in cross section and partly perspective,showing the third embodiment of the invention.

FIG. 7 is a perspective view relating to a fourth embodiment of theinvention.

FIG. 8 is a detail view of a component of the fourth embodiment of theinvention.

FIG. 9 is a pictorial view showing the fourth embodiment of theinvention.

FIG. 10 is a perspective view of a further embodiment of a filteraccording to the invention.

FIG. 11 is a pictorial view, partly in perspective and partly in crosssection, of a further embodiment of the invention.

FIG. 12 is a pictorial view, partly in perspective and partly in crosssection, of a further embodiment of the invention.

FIGS. 13 and 14 are pictorial views of an embodiment of the inventionfor blocking debris in the pulmonary artery.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 illustrates one embodiment of a filter 2 according to theinvention composed of a wire framework 4, made of a memory metal such asnitinol, and a filter fabric 6 of appropriate pore size, supported by aframework 4.

Filter 2 has a generally cylindrical structure with a small diameterend, at the top in FIG. 1, and a large diameter end, at the bottom inFIG. 1. In the expanded state of filter 2, the diameter of the smalldiameter end can be in the range of 18-26 mm and the maximum diameter ofthe large diameter end can be of the order of 35 mm.

According to a presently preferred embodiment of the invention, thelarge diameter end of filter 2 is formed to have a generally oval shapewith a major diameter of about 40 mm and a minor diameter of the orderof 30 mm. This allows the lower end of the filter to better conform tothe somewhat oval shape of a normal aorta.

Of course, the dimensions of filter 2 can be varied to conform to aortashaving different sizes, for example in children.

Filter 2 has a form defined by an outwardly bowed arcuate generatrix ofrotation about the longitudinal axis of filter 2 such that the wall ofthe filter bows outwardly, as shown in FIG. 1.

The framework of the illustrated embodiment is composed of a single wirethat includes a ring 4 a at the small diameter end, a series oflongitudinal struts, or ribs, 4 b, and a control portion 4 c thatextends to a location outside of the patient's body to allow theposition of filter 2 to be controlled by medical personnel. Theframework further includes a circumferential band 4 d at a locationbetween the small diameter end and the large diameter end. The frameworkmay also include a circular or oval nitinol ring extending around thelarge diameter end and bonded to the lower ends of ribs 4 b.

Filters composed of a framework of memory metal, e.g. nitinol, wires canbe constructed to present a radial expansion/compression ratio of 8:1,or more. Therefore, they will be held, in a compressed state in a sheathor tube having an inner diameter preferably equal to or greater than ⅛the desired expanded diameter of the large diameter end of the filter.

While FIG. 1 shows the framework to be provided with four ribs 4 b, afilter framework in accordance with the present invention can have manyother configurations and can, for example, be provided with six or moreribs 4 b. The framework can also be made of individual wires that aresoldered or otherwise secured together. In addition, control portion 4 ccan be a single wire or can be composed of two, four, or more wires,each connected to ring 4 a at a respective location such that the wiresare distributed, preferably at uniform intervals, around ring 4 a.

The structure shown in FIG. 1 further includes a guidewire 10 having adistal end soldered or otherwise secured to the interior surface of band4 d. The purpose of guidewire 10 will be explained below with referenceto FIG. 2.

Filter fabric 6 can be of any medically acceptable material havingappropriate mechanical properties and pore size suitable for trappingdebris while allowing the passage of blood therethrough. Examples ofsuitable materials for the framework and the filter fabric are describedin, for example, U.S. Pat. No. 7,214,237, the entire disclosure of whichis incorporated herein by reference.

FIG. 2 illustrates all of the components of a system for implanting aprosthetic aortic heart valve while preventing the passage of embolicdebris.

The components shown in FIG. 2 will be described in conjunction with adescription of the manner in which they are used.

In FIG. 2, filter 2 is shown in position in the patient's aorta 20 withthe base, or large diameter end, of filter 2 located downstream of tothe defective aortic valve 36.

The apparatus associated with filter 2 includes a guidewire 30 that isintroduced transcutaneously and then along a blood vessel path into theaorta and through the center of the native or previously implanted heartvalve. Guidewire 30 is then used to guide the introduction of a sheath,or tube, 32 along the same blood vessel path and into aorta 20 to bringthe distal end of sheath 32 adjacent the existing valve. Duringintroduction, filter 2 is collapsed within sheath 32. Then, when sheath32 has been brought into the desired position in aorta 20, for exampleadjacent the interface between the aorta and the existing heart valve,guidewire 30 can be withdrawn and sheath 32 can be withdrawn, at leastby a distance to not interfere with the valve implantation procedure,while filter 2 is held in place by acting on control portion 4 c, or theplural control wires, from outside the patient's body so that filter 2is freed from sheath 32. Filter 2 is thus automatically deployed, orexpanded, and placed in the position and configuration shown in FIG. 2,where the large diameter end of filter 2 is preferably downstream of thecoronary artery entrances to assure that blood flow to those arterieswill not be impeded by debris accumulating on fabric 6. However, filter2 may alternatively be deployed at a location above the coronaryarteries, close to the descending aorta.

Sheath 32 also contains a catheter 40 provided at its distal end with alow compliance, or noncompliant, blocking balloon 44. Catheter 40 alsoincludes, in a conventional manner, a balloon inflation lumen incommunication with balloon 44. Catheters provided with such lumens arewell known in the art. One example being U.S. Pat. No. 7,169,171, theentire disclosure of which is incorporated herein by reference. Catheter40 may have a diameter as small as 4 Fr. (1.3 mm).

After filter 2 has been deployed, catheter 40 is advanced alongguidewire 10 to bring balloon 44 to the location 44 a shown in brokenlines in FIG. 2. At this time, balloon 44 may be partially of fullydeflated. After balloon 44 has been brought to position 44 a, it may bepartially inflated by introduction of a radioactive contrast, orradiopaque, fluid, the purpose of which will be described below.

At a time after filter 2 has been deployed, guidewire 30 and sheath 32can be withdrawn from the patient's body.

Then, an assembly 60 for implanting the prosthetic heart valve isintroduced into the aorta, preferably, but not necessarily, via adifferent blood vessel path, by first passing a guidewire 62 along thatblood vessel path through the center of filter 2 and through theexisting heart valve. Assembly 60 includes, in addition to guidewire 62,a sheath, or tube, 64 and a system 66 including the prosthetic heartvalve and components for deploying it

After guidewire 62 is put in place, tube 64 is introduced into the aortaover guidewire 62 to a location adjacent filter 2, after which system 66is extended out of tube 64 and through ring 4 a of filter 2 and alongthe central orifice defined by filter 2, for implanting the prostheticheart valve. System 66 and one suitable manner in which it is used toimplant a prosthetic heart valve are all described in detail in U.S.Pat. No. 7,585,321, the entire disclosure of which is incorporatedherein by reference.

Valve assembly 60 can be inserted by puncturing an artery in the groinand advancing it upwards through the femoral artery and the aorta,followed by advancing system 66 through the existing valve.

The valve assembly could also be introduced through either the right orleft subclavian artery, which normally supplies an upper extremity.Consequently, there is the option of introducing sheath 32 and filter 2through either subclavian artery or through the femoral artery. Ingeneral, it is presently preferred to use one of these paths, thesubclavian artery or femoral artery, for introducing sheath 32, and theother of these paths for valve assembly 60. Since sheath 32 can have asmaller diameter, it might be advantageous to advance it through thesubclavian artery path.

It is presently believed by workers in the art to not be desirable touse the same route for introducing both the valve implantation assemblyand the filter assembly due to the fact that every trial done so far hascriticized the valve assembly alone as being relatively thick andtraumatic in the process of puncturing the artery. The only acceptablesingle route, which is not favored by patients, is to puncture theheart. For all these reasons, the diameter of valve assembly 60 has beenreduced in Europe to 18 mm, although this is not yet approved by theUSFDA.

It is important to note that the valve assembly is a cylindrical,relatively rigid structure below which the valve hangs, crimped on anangioplasty balloon, and that expansion of the valve is produced byinflating the angioplasty balloon in the case of the Edwards device andby pulling on the valve using nitinol bands in the case of a Medtronicdevice.

Neither of these techniques interferes with the use of the filterassembly according to the present invention, which serves to isolate thecarotids and other parts of the blood circulatory system from debristhat is released during and after implantation of the prosthetic valve,regardless of which valve implantation technique is used.

During implantation of the heart valve, tube 64 can bear against theopening at the top of filter 2 to help prevent the passage of embolicdebris and to stabilize the position of the filter. Filter 2, sheath 32and wire 10 are oriented to cause wire 10 to extend into filter 2,adjacent ring 4 a, at a location to not interfere with the positioningof tube 64.

Balloon 44 may be partially inflated with radioactive contrast fluidbefore withdrawal of the components 66 for implanting the heart valveand tube 64; and immediately after withdrawal of those components,balloon 44 is further inflated, if this was not previously done, andpulled back by acting on catheter 40 from outside the patient's body tocause balloon 44 to block the small diameter opening of filter 2. Thepresence of radioactive contrast fluid allows the position of balloon 44to be monitored fluoroscopically.

Inflated balloon 44 acts to close the smaller diameter hole in filter 2as soon as the prosthetic valve introduction system is retracted out ofthe filter, thus enabling debris to be trapped adjacent the smallerdiameter end of the filter.

Then, after a suitable period of time has elapsed, during which debriscan become trapped in filter 2, filter 2 and balloon 44 are drawn intosheath 32 by pulling on control portion 4 c, or the plural controlwires, if provided, and catheter 40 and tube 64, along with all of theassociated components, are withdrawn from the patient's body.

More specifically, balloon 44 will remain inflated and lodged in thesmaller diameter opening of filter 2 during an initial phase ofwithdrawal so that filter 2 and catheter 40 will be pulled toward sheath32 as a unit. Then, when the smaller diameter end of filter 2 reachessheath 32, balloon 44 will be deflated and catheter 40 may be partiallyor fully retracted so that balloon 44 moves out of contact with filter2. Then, filter 2 can be retracted into sheath 32; and then sheath 32,containing catheter 40 and filter 2, can be fully withdrawn from thepatient. During this withdrawal procedure, suction may be appliedthrough sheath 32 to assist the removal of any embolic debris fromfilter 2.

As an alternative to using a wire 10 to introduce balloon catheter 40,it would be possible to simply use a small diameter catheter with aballoon at the end, surrounding the catheter wall and communicating witha balloon inflation lumen formed in the catheter, to close the opening,or orifice, at the top of filter 2 as soon as valve assembly 60 ispulled out of the filter, thereby preventing escape of emboli. Thissmall diameter catheter may be introduced with the aid of a guidewirethat extends though the catheter.

The fact that filter 2 is open at the top offers the advantage ofpreventing the filter from being blown out of position by the relativelyforceful blood flow being produced by the heart as it pumps the blood.

The radiopaque fluid used to inflate balloon 44 will enable the balloonto be readily observed.

Inflated balloon 44 will also serve as a means for partially alteringthe configuration of the filter and making it parallel to and in linewith sheath 32 to facilitate retraction of filter 2 into sheath 32 aftercompletion of the procedure.

FIGS. 3 and 4 show a filter 72 according to a second embodiment of theinvention that can provide improved protection against the escape ofembolic debris. Filter 72 has a generally cylindrical structure, atleast when expanded, and is composed of a framework presenting twoportions: a lower portion between a ring 74 a at the lower end of thefilter and a ring 74 c at the upper end of the lower portion; and anupper portion extending between ring 74 c and a ring 74 f at the upperend of the filter.

The lower portion is also composed of a series of longitudinal struts,or ribs, 74 b extending between rings 74 a and 74 c, and acircumferential band 74 d at a location between rings 74 a and 74 c.Preferably, as in the case of the embodiment of FIGS. 1 and 2, ring 74 ais shaped so that in its expanded, or deployed, state, it has an ovalform with major and minor diameters of the order of 40 mm and 30 mm,respectively.

Struts 74 b, like struts 4 b of FIGS. 1 and 2, are preformed to curve inthe manner illustrated when the filter is deployed, in which case theexternal surfaces of struts 74 b are outwardly convex.

The upper portion of filter 72, between rings 74 c and 74 f, is providedwith a plurality of longitudinal struts, or ribs, 74 e. Preferably,struts 74 e curve in the opposite direction from struts 74 d so thatstruts 74 e are outwardly concave when the filter is deployed. However,struts 74 e can also be constructed to have a straight form when thefilter is deployed.

The framework of filter 72 is completed by, preferably, four wires 74 gconstituting a control portion performing the same function as controlportion 4 c shown in FIGS. 1 and 2. The provision of four wires 74 gallows for the possibility of controlling the positioning of the filterin the aorta.

Like the embodiment shown in FIGS. 1 and 2, the filter shown in FIGS. 3and 4 includes guidewire 10 whose distal may be soldered or otherwisesecured to the inner surface of band 74 d. The purpose of guidewire 10is essentially the same of that of the guidewire 10 described withreference to FIGS. 1 and 2.

Also like the embodiment of FIGS. 1 and 2, a filter fabric is suitablysecured to and supported by the framework composed of components 74 a-74f. Also as in the case in the embodiment shown in FIGS. 1 and 2, thereis no fabric in the planes enclosed by rings 74 a and 74 f.

Also shown in FIG. 3, in broken lines, is the distal end of tube 64. Atleast ring 74 f is dimensioned to allow entry of tube 64 into the regionenclosed by filter 72 and wires 74 g. Ring 74 f, in the deployed stateof filter 72, could have a larger diameter than ring 74 c if needed toaccommodate tube 64.

Preferably, ring 74 f is dimensioned to provide a close fit with tube64. Optionally, the distal end of tube 64 can be slightly tapered toallow introduction of tube 64 into the upper portion of filter 72, whileassuring the establishment of a tight fit with ring 74 f, and possiblyto provide a sealed connection between tube 64 and ring 74 f, therebypreventing the escape of embolic debris from filter 72 during valveimplantation.

The manner in which filter 72 is used will be explained with referenceto FIGS. 2, 3 and 4.

Filter 72 is employed together with system 60, sheath 32, catheter 40and low compliance or noncompliant balloon 44, all of which are shown inFIG. 2, and the operation of which has been described above.

After filter 72 has been installed and positioned to surround the entireregion through which the replacement valve will be deployed, catheter 40carrying balloon 44 is advanced over guidewire 10 to the location shownin FIG. 4 and tube 64 is introduced over guidewire 62 so that the distalend of tube 64 penetrates at least the upper part of the upper portionof filter 72, and preferably forms a seal with ring 74 f. Tube 64 andcatheter 40 essentially block the upper end of the upper portion offilter 72. Since catheter 40 has a relatively small diameter, of theorder of 1 mm, only a minimal gap will exist at the top of upper portionof filter 72 so that escape of debris from filter 72 will be minimal, ifany.

Then, system 66 is operated to install the replacement heart valve.

At the completion of this operation, after system 66 has been withdrawnback into tube 64, balloon 44 is at least partially inflated andcatheter 40 is withdrawn to bring balloon 44 into contact with ring 74c. Before or after balloon 44 has been brought to the proper position,it may be further inflated in order to form a tight seal at the locationof ring 74 c. Then assembly 60 can be fully withdrawn, after whichfilter 72, with balloon 44 still in place and inflated, begins to bewithdrawn into sheath 32 by pulling on control wires 74 g.

After the top portion of filter 72 has been introduced into sheath 32,balloon 44 is deflated while, preferably, suction is produced withinsheath 32 in order to withdraw any debris being held within filter 72.

After deflation of balloon 44, filter 72 and catheter 40 are completelywithdrawn into sheath 32, and sheath 32 can then be withdrawn from thepatient's body.

The invention as described above offers a number of other advantages.For example, it will allow injection of clot lysing material into thefilter and if catheter 40 is provided with an orifice above filter 2, itcan be used to continuously monitor the arterial blood pressure.

The filter disclosed herein may also be used to trap embolic debris, orblood clots, in other procedures, such as in treating children or youngadults with congenital heart disease who have pulmonary stenosis and onwhom is performed a similar procedure that may generate blood clots.

In FIGS. 2 and 4, a catheter carrying a blocking balloon and a tube 64for the valve delivery system both pass through the opening at the topof the filter. While it is obvious that there will be a gap presentaround the catheter, the size of the gap would be no more thanapproximately 1/24 of the diameter of tube 64. However, in the case offilter 72, balloon 44 will form a near-perfect seal with ring 74 c. bothbefore the withdrawal of system 66 carrying the valve and thereafter.The technique would be to inflate the balloon at the junction with thevalve carrying device and track both these structures upwards duringtheir withdrawal. At a time not later than the point in the procedurewhen the valve delivery sheath is about to exit the bottleneck, theballoon would be fully expanded to completely close the orifice throughwhich it is retracted, thereby preventing escape of emboli both in theearly and late phases of valve/sheath withdrawal. When this isaccomplished, and the sheath of the valve is separated from the bottleneck carrying the balloon, the correct procedure would be to advancesheath 32 carrying the bottleneck from the side arising from thesubclavian artery and collapse the balloon and catheter into sheath 32.The balloon would have appropriate consistency which allows it to beoptimally in contact with the nitinol sheath; if it is underinflated orhas a low pressure it may not prevent emboli from going upwards betweenthe balloon and nitinol sheath. If it is excessively stiff and at a highpressure, it could stretch and damage the nitinol filter.

Balloon 44 should be one with a reasonably low compliance such that itdoes not rupture and does not expand the bottle neck, which ispreferably made of nitinol but has a firm surface.

The components of the embodiment shown in FIGS. 3 and 4 can beintroduced into the aorta over the same paths as described withreference to the embodiment of FIGS. 1 and 2.

A further embodiment of the invention is shown in FIGS. 5 and 6.

According to this embodiment, components 60 and 80, to be describedbelow, can be introduced along the same path, for example along thefemoral artery and into the aorta via an incision made in the groin, orthrough one subclavian artery, as described earlier herein.

The components shown in FIG. 5 include a guidewire 62 that is introducedfirst into the ascending aorta (20 in FIG. 2), to a point close to thevalve that is to be replaced, or to a point above the coronary arteries.Then, guidewire 62 is used to introduce a first sheath 64, which mayhave a diameter of the order 7 mm, and the distal end of sheath 64 isalso brought to a point in the ascending aorta, after which guidewire 62may be withdrawn, and a second sheath 68, which may have a diameter ofthe order of 6 mm, is introduced into sheath 64.

Sheath 68 contains a filter 80 somewhat similar to filter 2 shown inFIGS. 1 and 2. In the illustration provided in FIG. 5, filter 80 is heldin a radially compressed state in sheath 68.

Filter 80, which will be described in greater details below withreference to FIG. 6, is provided with two control wires 82 that extendthrough sheath 68 to a location outside of the patient's body.

After sheath 64 has been brought to its desired position in the aorta,sheath 68 will be advanced to bring its lower, or distal, end to alocation close to the defective heart valve, at least approximatelywhere the lower end of filter 80 is to be deployed. Then, sheath 68 isretracted while filter 80 is held in place by a holding force, possiblymanual, on control wires 82. As filter 80 thus exits the lower end ofsheath 68, the filter expands while it is being deployed to bring it tothe desired position to collect debris.

Then, sheath 68 may be withdrawn from the patient's body.

Referring now to FIG. 6, which shows filter 80 in its deployed state, itwill be seen that filter 80 is compose essentially of a framework thatincludes an upper ring 84, a lower ring 86 and longitudinal struts 87,all preferably made of a type of a memory metal such as nitinol. Thesides of filter 80 are covered with a suitable filter fabric having apore size of, for example, 110 μm. Filter 80 is open at the top and thebottom and has a generally frustoconical shape when deployed.

Filters having a nitinol frame can generally expand radially by amaximum factor of 8 and filter 80 is dimensioned so that in thedeployed, or expanded state, lower ring 86 has a diameter of the orderof 32 mm and upper ring 84 has a diameter of the order of 7 mm. Sheath64 is brought to a position in which, as shown in FIG. 6, the lower endof the sheath 64 contacts ring 84.

After filter 80 has been thus deployed and sheath 64 has been broughtinto the position shown in FIG. 6, a system 66, described earlierherein, will be introduced through sheath 64 and then through filter 80,after which system 66 will be operated in a known manner to implant theprosthetic valve.

Typically, introduction of system 66 will be aided by a guidewire suchas guidewire 62 shown in FIG. 2 of the application drawing, which willbe introduced in order to guide system 66 past the defective heartvalve.

During implantation of the heart valve, debris will be released and thisdebris will be confined by filter 80 and will be carried off with bloodthrough sheath 64 to a suction device located outside of the patient'sbody. This blood and debris can pass through at a conventional devicesuch as a Coulter counter, which detects and counts the debrisparticles. Suction will be continued until the output of the measuringdevice indicates that no further debris is present in the blood flow.

With the arrangement shown in FIG. 6, sheath 64 helps to stabilize theposition of filter 80.

After such an indication has been produced, filter 80 can be withdrawn,by acting on the control wires 82, into sheath 64 and all components canthen be withdrawn from the patient's body.

After filter 80 has been deployed at the desired location, a guidewire(not shown) is introduced, for example through the groin or thesubclavian, and then passed though ring 88 into the region enclosed byfilter 80.

Outside of the patient's body, debris in the blood exiting thought thetop of filter 80 can be filtered out of the blood and the filtered bloodcan be returned to the patient's circulatory system, as will bedescribed subsequently herein.

A further embodiment of the invention is illustrated in FIGS. 7, 8 and9.

FIG. 7 shows a filter 90 having a generally conical form that is open atits large diameter lower end and closed at its upper end, and the sidesof which are covered with filter material, or fabric, filter 90 thusbeing in the general form of a cone.

Filter 90 is provided with a control wire 92 at its apex, where it isclosed. Filter 90 can be introduced through a subclavian artery, forexample the left subclavian artery.

Filter 90 is provided with an entry cone 100 and a side opening 104 inwhich filter fabric is not present. Side opening 104 is closed by aseries of flaps of a suitable material, constructed to normally beclosed, together with a tube 108, which may be corrugated, and which isopen at its inner end 112, as shown most clearly in FIG. 8. Entry cone100 may be corrugated, as shown, and dimensioned to bring the distal, orlower, end of cone 100 to the plane of the open end of filter 80 and tothe center of the lower end.

Referring to FIG. 9, filter 90 is introduced into position in ascendingaorta 20 by means of a sheath 120 that performs essentially the samefunction as sheath 32 shown in FIG. 2, except, in this embodiment,components 40, 44 and 44 a are not provided. After filter 90 has beendeployed, essentially in the manner described earlier therein, assembly60 is introduced, possibly through the femoral artery and the descendingaorta, and is inserted into cone 100 through opening 104. Preferably,cone 100 is dimensioned so that at least the lower end thereof forms aseal with tube 64.

Then, in the manner described previously, for example with respect toFIG. 2, the guidewire associated with assembly 60 is introduced throughthe defective heart valve and assembly 60 is then operated to implantthe new valve.

During implantation, sheath 120 may be placed in contact with filter 90to stabilize the position of the filter.

After implantation, suction is maintained through tube 64 to extractdebris mixed with blood and, as in the case of the embodiment of FIGS. 5and 6, the blood being suctioned is monitored to determine when alldebris has been removed.

Then, assembly 60 is withdrawn from the patient's body, filter 90 isretracted into sheath 120, and sheath 120, with retracted filter 90, iswithdrawn from the patient's body.

According to an alternative valve implantation procedure, the heart maybe punctured at its apex and valve assembly 60 can be inserted throughthe puncture opening in the apex from a location below the existingvalve. In this case, the filter structure shown in FIGS. 7-9 can be usedfor introducing valve assembly 60 and catheter 116. Sheath 120 can thenbe placed in contact with filter 90 to stabilize the position of thefilter.

In further accordance with the invention, a wall stent or stent graftmay be initially deployed to protect the aorta during valve implantationand an inflatable sheath may be employed in place of sheath 32 tofacilitate retraction of filter 2, 72, 80, 90. In addition, the filtermay be provided with additional structures to control blood flow fromthe heart in a manner to assure that the filter is not displaced by theforce of the blood flow. These features will be described in detailbelow.

Two well known stent-grafts are: the Cook Zenith Flex graft and theMedtronics graft for the ascending aorta.

In each embodiment of the invention, the framework may be coated orimpregnated with radiopaque material, or could be provided withindividual radiopaque studs, or beads, lining the top and/or the bottomrings of the filter framework to facilitate guidance of the filter toits desired position and introduction of wire 62. i.e. guidance ofsystem 66 through the hole at the top of the filter and into theexisting valve.

Filters according to the present invention may be positioned to surroundthe entire circumference of the valve that is deployed, with the resultof preventing blood clots from entering the coronary arteries.

In the case of the embodiment shown in FIGS. 7, 8 and 9, sheath 120 maybe introduced through one subclavian artery, assembly 60 may beintroduced through a femoral artery and catheter 116 may be introducedthrough a radial artery or the other subclavian artery.

A further embodiment of the invention is composed of a debris filter150, shown in FIG. 10.

The filter shown in FIG. 10 is somewhat similar to filter 80 shown inFIG. 6. Filter 150 is provided with control wires 152 corresponding infunction to control wires 82 shown in FIG. 6. Filter 150 is composed ofan upper ring 154, a lower ring 156 having, in a deployed state of thefilter, a larger diameter than ring 154, and longitudinal struts 158,all of these parts preferably being made of a type of memory metal suchas nitinol. Upper ring 154 is connected to wires 152. The sides offilter 150 are covered with a suitable filter fabric having a pore sizeof, for example, 100 μm, or more generally a pore size that will permitas free a flow of blood as possible, while retaining embolic debriswithin the filter.

The lower end of filter 150, enclosed by ring 156, is open to receiveblood and debris from the region being treated, such as the heart valveregion and the area of the aortic wall into which vein bypasses arecustomarily attached or implanted.

Filter 150 differs from filter 80 essentially only in that the upper endof filter 150, enclosed by ring 154, is covered with the same type offilter fabric as described earlier herein, with a pore size of, forexample 100 μm. The upper end of filter 150 may be provided with a smalldiameter ring 170 secured to ring 154 by at least four radial spokes174. The outer ends of spokes 174 are bonded to ring 154 in any suitablemanner to secure ring 170 in place. Ring 170 and spokes 174 may be madeof nitinol wires. Filter fabric is not present in the region enclosed byring 170.

Ring 170 is dimensioned to receive a small diameter tube, or catheter,176, which may have a diameter of the order of 5-6 Fr. and is preferablydimensioned to achieve a sufficiently close fit between ring 170 andtube 176 to prevent the escape of debris therebetween. Tube 176 may beof a type known as a “pigtail” catheter.

After filter 150 has been deployed at the desired location, a guidewire(not shown) is introduced, for example along the same path as filter150, and then passed though ring 170 into the region enclosed by filter150. Then tube 176 is passed over the guidewire and through ring 170,also into the region enclosed by filter 150.

Filter 150 is provided at its side with a plate 160 provided with athrough opening 162 that is not covered with filter fabric.

Tube 176 is employed to inject a contrast fluid that facilitatesvisualization of the surgery site, such as the aorta and the aorticvalve. It can also be utilized to work with a TAVI catheter assemblywhich is inserted through opening 162. Thus, the tube 176 and the TAVIcatheter can be used simultaneously to permit observation of the naturalvalve and to cross it, respectively.

After the need to inject contrast fluid has ended, tube 176 can bepulled up so that its lower end is still within filter 150 and so thatit continues to obturate the opening defined by ring 170. Tube 176 canbe connected to a suction device outside the patient's body to suctiondebris, inevitable accompanied by blood, through tube 176. Outside ofthe patient's body, debris can be filtered out of the blood and theblood can be returned to the patient's circulatory system

The device shown in FIG. 10 is intended to be employed together with avalve implantation assembly, such as assembly 60 shown in FIG. 2 anddescribed in detail earlier herein.

A procedure according to the invention, using the devices shown in FIG.10, along with a valve implantation assembly is performed in thefollowing manner.

A first guidewire is inserted along a blood vessel path to a point closeto the heart valve that is to be replaced and then a sheath, such assheath 32 shown in FIG. 2, is advanced over the guidewire. Then, theguidewire is withdrawn and a filter 150 is introduced through and out ofthe sheath to a location corresponding to that shown in FIG. 2. Thedelivery of filter 150 is controlled by control wires 152. Filter 150may be installed initially in the distal end of sheath 32, prior tointroduction of sheath 32 into the blood vessel. If ring 170 isprovided, the first guidewire cam be inserted through the hole enclosedby ring 170 prior to introduction into the blood vessel. If ring 170 andits associated hole are not provided, the first guidewire can beinitially threaded through side opening 162 and then through the bloodvessel

Then, a second guidewire, such as guidewire 62 shown in FIG. 2, isintroduced through a blood vessel path and directed through opening 162.Then, assembly 60 is introduced into the blood vessel path and tube 64or system 66 is caused to pass through opening 162 and is operated toimplant an artificial valve, as described above.

After the valve has been implanted, assembly 60 and guidewire 62 areremoved from the patient's body.

All of the guidewires employed in the practice of all of the embodimentsdisclosed herein may be any commercially available guidewires intendedfor use in blood vessels, such as Charter™ Guidewires marketed byNavilyst Medical of Marlborough, Mass.

The following table lists the blood vessel passages that can be used forintroduction of each of the devices described above.

FIG. DEVICE ARTERY  2 32 Subclavian  2A 32 Subclavian  5 62 Subclavian 6 (2A) 32 Subclavian  7 92 Subclavian or femoral  9 60 Femoral 10 (2A)150 Subclavian 11 180 Femoral

If, in the procedure described with reference to FIG. 10, the TAVIassembly and the filter sheath are introduced through the groin, thepigtail catheter can be introduced through the apex of the filtersimilar to that shown in FIGS. 10-12, in which the hole is located atthe top of the filter in the central area within the upper ring of thefilter.

It is important to point out that the TAVI catheter and the pigtailcatheter are in proximity to each other prior to and immediately afterthe valve is implanted. This is an essential part of the procedure whichensures appropriate positioning during the process of implanting thevalve. It is also to be noted that in either event, namely, using thesubclavian or the groin, due to the constraints of space, the TAVIcatheter assembly 60 and the filter enter through the same artery, withthe filter sheath being withdrawn from the artery before introduction ofthe valve implantation assembly 60, while, the pigtail catheter isintroduced through a different artery. This ensures that the diameter ofthe blood vessel in either case is not stretched to the point of injury.

In the case of the embodiment shown in FIG. 10, filter 150, in itsintroduction sheath, may be introduced through a femoral artery or asubclavian artery, and the TAVI catheter assembly (60 in FIG. 2) may beintroduced through a femoral artery or subclavian artery different fromthat used for introducing filter 150. Tube 176 may be introduced througha radial artery.

A further embodiment of a device incorporating a filter according to thepresent invention is illustrated in FIG. 11.

The embodiment shown in FIG. 11 is intended to be employed in connectionwith invasive procedures, such as open heart surgery, using instrumentsnot introduced through, for example, the aorta.

A purpose of this embodiment is to avoid the adverse, and potentiallyfatal, effects of bypass surgery caused by the migration of emboli intothe brain, resulting in strokes and cognitive disorders.

This embodiment includes a filter 302 that will be deployed at alocation downstream of the surgical site. Filter 302 is somewhat similarin form to filter 2 shown in FIGS. 1 and 2, filter 302 having a largediameter end 304 and a small diameter end 306, and the filter beingopened, i.e. not provided with filter fabric, at both ends 304 and 306.Small diameter end 306 is secured to a suction tube 308.

Large diameter end 304 may have a deployed diameter of 32-40 mm, whilesmall diameter end 306 and tube 308 may have a diameter of the order of4 mm.

The proximal end of tube 308, i.e. the end that will be outside of thepatient's body, is secured to a filter 312. The assembly composed offilter 302 and tube 308 may be introduced through a suitable sheath 320into an artery to a point downstream of a location where debris will beproduced by the surgical procedure and upstream of vessels that carryblood to the brain.

When filter 302 has been introduced to the desired location anddeployed, and the surgical procedure is being performed, debris producedby the procedure will be conveyed, along with blood, into filter 302. Aportion of the blood will then pass through the filter mesh, or fabric,that covers the circumference of filter 302 between ends 304 and 306while the debris, along with some blood, will flow through smalldiameter end 306 and tube 308 to filter 312. In filter 312, debris willbe separated from blood and the filtered blood may then be conductedinto an artery or vein to be returned to the circulatory system. Filter312 may be constructed according to principles already well known in theart.

The device shown in FIG. 11 may be introduced through any suitableartery. For example, in the case of open heart surgery, filter 302 maybe introduced into the aorta along a path from an incision in the groinor through the subclavian artery.

Filter 302 could also be introduced on the right side of the heart inthe pulmonary artery as a potential means of preventing blood clots fromentering the lungs and for right heart surgery. The device could beintroduced in this case through a peripheral vein.

In all cases, filter 302 would be deployed downstream from the locationswhere emboli would be produced during the surgical procedure.

FIG. 12 shows a modified version of the device of FIG. 11 and embodies afilter 402 with an open end 404 at the bottom and an upper end 406provided with an opening, similar to that shown in FIG. 10, but withoutplate 160 and opening 162. The upper end 406 is closed by filter fabricmaterial and has a central metal ring providing an orifice and spokesthat connect the ring to the upper end of the filter. The orifice is notcovered with filter fabric and allows the passage of a catheter 408having a diameter of 5-7 Fr., and preferably 5-6 Fr., which can beintroduced through a sheath 420 that was preliminarily passed throughthe radial artery with the aid of a guidewire, and then passed into thefilter. This catheter 408, depending on what is needed, can either be apigtail catheter or can be a fiberscope or an ultrasound device whichcan be used to view the aorta and the location of the valve and thewalls of the aorta. Thus, this device can be used through its entrancesheath 420 in the arm to obtain pictorial representations of thecondition of the aorta and the aortic valve, or other part beingtreated. This would be done prior to open heart surgery and could bereplaced with a 5-7 F pigtail catheter, which is used to drain debrisexiting from the apex of filter 402. The proximal end of catheter 408will be attached, outside the patient's body, to a 3-way stop cock 410through which contrast fluid can be introduced from a supply tube 412,or through which debris and blood could be passed to a filter 414, asdescribed with reference to FIG. 11. This device will serve to minimizethe spread of debris to the brain and body and enable blood flow tocontinue through 100 μm holes in the fabric. Filter 414 could beassociated with a suction device to help suction debris out of filter402.

The assembly shown in FIG. 12 differs from those used for TAVI, i.e,those involving introduction of a replacement heart valve through thearteries. Sheath 420 and tube 408 can be introduced through a subclavianartery, or a radial artery in the arm, or the groin. The exiting debrisand blood is passed through an external filter and the blood is returnedinto the body as described in the case of the TAVI filter. This isdifferent from the debris removal described in connection with TAVIprocedures.

The assemblies shown in FIGS. 11 and 12 can be introduced via a femoralartery or a subclavian artery.

In all of the procedures employing filters according to the invention,any opposition to deployment and positioning of the filter can beminimized by temporarily halting or reducing the flow of blood from theaorta. This can be achieved, for example, by employing a pacemaker toproduce a high pacing rate, for example of the order of 220beats/minute.

The present invention provides the possibility of using at most two tothree entry passages to completely implant and stabilize the filter,trap and withdraw debris and deploy an artificial valve. These entrypoints can be selected from one groin and the radial artery that leadsinto the subclavian to carry the pigtail catheter for introducingcontrast fluid, or one groin, which carries the TAVI catheter and thesheath for implantation of the filter. In the event that the both groinsare blocked and cannot be used, use can be made of one subclavian todeploy the filter and TAVI catheter and the other subclavian tointroduce and advance the pigtail catheter. In either of these cases,the ability exists to perform two processes: To use the TAVI catheterand filter through a single groin or subclavian and the other to implantthe pigtail catheter through the opposite groin or subclavian. In eithercase the ability to use the TAVI catheter with the filter depends on theability to initially advance the filter with its sheath which encloses aguide wire, to deploy the filter and after this, to withdraw the sheathwhich surrounds the guidewire all the way to the origin of the point ofinsertion of the filter, thus, creating adequate space to advance theTAVI catheter with or without its own guide wire alongside thisguidewire and to enter the orifice described in the filter.

However, the TAVI catheter can be inserted into the right groin and thefilter can be inserted into the left groin or vice versa or underexceptional circumstances into the right or left subclavian. It wouldstill be possible to use the radial artery on the right or left side toimplant the pigtail catheter depending on the points of insertion of thefilter and the TAVI catheter. These circumstances will depend on therecently developed 12 Fr. TAVI catheters and changes in theexpansibility of the modified nitinol to create the filter. These arecurrently not in common use.

Filters according to the present invention can have a radial expansionratio of 8:1. If the compressed diameter is, for example, 4.5 mm, theexpanded filter can obturate the aorta with a lower ring such that it isinserted to apply pressure on the circumference of the aorta tostabilize it.

The catheter that may be a pigtail catheter can be used both forinjecting contrast fluid for withdrawing debris from the filter in asafe and sterile way into an artery of the wrist, namely, the radial,which allows the observer to visually see the debris and subject it toquantitative and qualitative analysis and/or filtration. The debris canbe analyzed by a cell counter such as a Coulter counter, which canenable a temporal estimation of debris production and clearance.

Relative to the use of a filter on the right side of the heart, it ispossible to use a filter similar to the one described previouslycomposed of nitinol and fabric and introduced through a sheath, whichfilter does not incorporate orifices, or openings, as previouslydescribed. This filter is introduced, enclosed by a sheath, through avein which carries blood to the heart and which is located in an arm,the neck or the legs.

The sheath and filter can be introduced under fluoroscopic control intothe right side of the heart, traversing one of the two main veinsentering the heart and is manipulated under fluoroscopic control intothe pulmonary artery which supplies the lungs. The filter is deployed ina similar manner by withdrawing the sheath and allowing it to stabilizein the pulmonary artery. Since the pulmonary artery divides into leftand right branches, these arteries to the left and right lung areprotected from emboli. This technique is particularly applicable incardiac surgery for congenital heart disease to prevent blood clots fromentering the lungs, which is a known complication of this type ofsurgery. The filter is deployed and removed using the same techniquesexplained above with the TAVI filter and the other described filters,namely, by pulling the filter into a sheath to close it or expressingthe filter out of the sheath, to deploy it.

FIGS. 13 and 14 illustrate a further embodiment of the invention forblocking the flow of debris through the pulmonary artery during asurgical procedure performed on the heart, such as congenital heartsurgery.

As shown in FIGS. 13 and 14, this embodiment includes a sheath 512having a diameter selected to be compatible with the dimensions of thepatient's blood vessels. Sheath 512 carries, near its distal end, aballoon 514 that is provided to assist guidance of the sheath to bringthe distal end to a point in the pulmonary artery. As shown in FIG. 13,sheath 512 is constructed, similar to a Swan-Ganz sheath, or catheter,to be capable of being inserted through a vein in the arm or neck and tothen be guided through the superior vena cava, the right atrium, thetricuspid valve, the right ventricle, and the pulmonary valve of thepatient's heart.

The embodiment further includes a wire 516 that will be guided throughsheath 512 and that carries, at its distal end, as shown in FIG. 14, afilter composed of a framework 518 and a filter mesh material 522constructed as in the case of the embodiments previously described, toallow the passage of blood, while blocking the flow of debris. Thefilter further includes a plurality of wire struts 530 secured,preferably in a sliding manner, as shown by opening 534, to wire 516.

Struts 518 and 530 are preferably made of nitinol.

The filter is constructed, similar to the filters described earlierherein, to have a radially compressed state and a radially expandedstate and to automatically assume the radially expanded state whenunconstrained.

In the embodiment shown in FIGS. 13 and 14, the filter will be housed insheath 512 until the distal end of sheath 512 reaches a desired locationin the pulmonary artery. Then, wire 516 will be advanced while sheath512 is held stationary, to cause the filter to emerge from the distalend of sheath 512 and assume its radially expanded state, as shown inFIG. 14. The filter is dimensioned to extend entirely across thepulmonary artery in order to trap any debris released during heartsurgery and thus prevent debris from entering the patient's lungs.

After the medical procedure has been completed and the flow of debrishas subsided, the appliance may be removed in one of the following ways:

Wire 516 will be pulled back while sheath 512 is held stationary towithdraw the filter into sheath 512, while the filter is brought to itsradially compressed state with the aid of struts 530, or sheath 512 willbe advanced over the filter to place the filter in its radiallycompressed state within sheath 512. Then, sheath 512, with the filterheld therein, is withdrawn from the patient's body in the reversedirection along the insertion path; or

A slit is made in the pulmonary artery to access the filter, the filteris radially compressed and wire 515 is cut by suitable instruments,after which the filter is withdrawn through the slit in the artery.Then, sheath 512 and the remainder of wire 516 are withdrawn in thereverse direction along the insertion path.

Sheath 512 may, for example, have a diameter of 10 Fr. The proximal endof sheath 512 may be connected to a suction device 550 that helps tosuction debris collected in the filter.

Suction device 550 may, in turn, be connected to an arrangement such ascomponents 410, 412 and 414, as shown in FIG. 12. Debris leaving filter414 may pass through a Coulter counter to monitor the presence ofdebris.

With respect to all embodiments of the invention, if a filter having alarger compression ratio, e.g. 16:1, is used, the filter sheath may havea correspondingly smaller diameter.

The presently disclosed embodiments are therefore to be considered inall respects as illustrative and not restrictive, the scope of theinvention being indicated by the appended claims, rather than theforegoing description, and all changes which come within the meaning andrange of equivalency of the claims are therefore intended to be embracedtherein.

1. A device for trapping debris produced during a surgical procedureperformed on a patient, said device comprising: a collapsible anddeployable filter for blocking debris and passing blood in a bloodvessel in a patient's body, a guidewire connected to said filter, and asheath in which said filter is housed, said filter comprising; aframework of a flexible material, said framework being constructed tohave a radially compressed state, in which said framework is radiallycompressed by radial deforming forces, and a radially expanded state;and a flexible filter material secured to said framework and havingpores dimensioned to prevent the passage of debris therethrough whileallowing the passage of blood, wherein: said filter has, in the radiallyexpanded state of said framework, a generally conical form with a largediameter end, a closed end opposite to said large diameter end, and aside surface extending between said large diameter end and end; saidflexible filter material covers the entirety of said side surface fromsaid large diameter end to said closed end; and said large diameter endis open to receive blood and debris and is dimensioned to prevent flowof blood between said large diameter end and the blood vessel wall whensaid framework is in the radially expanded state; said sheath having adistal end and having a length and flexibility sufficient to extendthrough the patient's blood vessels and heart from a point outside thepatient's body to the patient's pulmonary artery; said guidewireextending through said sheath and having a distal end connected to saidclosed end of said filter with said filter being oriented, wherein saidfilter is extendable from said distal end of said sheath and is movable,with the aid of said guidewire, between said radially compressed statewithin said sheath and said radially expanded state when said filter isextended from said distal end of said sheath, and said filter isoriented such that said large diameter end faces said distal end of saidsheath when said filter is extended from said distal end of said sheath.2. A method for blocking debris in a pulmonary artery of a patientundergoing a surgical procedure on the heart, using said device asdefined in claim 1, said method comprising: advancing said sheath withsaid filter in the radially compressed state within said sheath, througha vein and the heart of the patient to bring said distal end of saidsheath into the pulmonary artery of the patient; bringing said filter toa location in the pulmonary artery of the patient outside of said distalend of said sheath to move said filter to the radially expanded state;performing the surgical procedure; and after the surgical procedure,withdrawing said device from the patient's body.